compression number on 73 envinrude????

[catfish charlie]

hi guys,<br />im in the process of finding a replacement outboard for my merc.,which blew up. i found a 73 envinrude and the compression numbers are as follows.. 106..106..117 ..does it sound ok. i dont want to get another outboardthat needs rebuilding.. are these numbers low ? i have heard of someone outboards having 125-145 on compression..what you think?

 

[MCM]

Re: compression number on 73 envinrude????

Hi, as I understand it all your readings should be within 10 psi of each other, the 11 psi diff. in that one cyl an indication of an underlying problem.<br /><br />It sounds like you'ld be buying something you'll end up working on in the near future.<br /><br />Mike

 

[JB]

Re: compression number on 73 envinrude????

Those are decent numbers, and within OMC spec, if it is a 3 cylinder engine. The OMC spec is +/- 15%.<br /><br />Mind telling us what engine that is?

 

[catfish charlie]

Re: compression number on 73 envinrude????

all is i know its a 100 hp 73 evinrude

 

[MCM]

Re: compression number on 73 envinrude????

What are they asking for the motor?<br /><br />Mike

 

[Solittle]

Re: compression number on 73 envinrude????

If you get it do a decarb and recheck the compression. It is not that bad as is.

 

[JB]

Re: compression number on 73 envinrude????

100HP?? Compression numbers on 3 cylinders??<br /><br />That does not compute, Charlie. The 'Rude 100s were all V4s.<br /><br />Somebody is blowing smoke here.<br /><br />Do NOT, under any circumstances at any price, buy that engine until you get accurate and useful information.<br /><br />Start with the model number and compression numbers on 4 cylinders. Then get a demo under load.<br /><br />Good luck.

 

[catfish charlie]

Re: compression number on 73 envinrude????

yes i know. i went to check motor myself. the left bank was between 118-120 and the right bank was between 106-110. why are the right banks lower.does that meansome problems. thanks alot

 

[djzyla1980]

Re: compression number on 73 envinrude????

Since both of the right banks are lower... I would almost suspect a blown head gasket... or something along that line. If one of those cylinders were reading low I would suspect otherwise like rings, etc.<br /><br />The only way to really tell what going on in that side is to pull the head.

 

[JB]

Re: compression number on 73 envinrude????

A range of 106psi to 120psi is acceptable according to OMC. 15% would be an 18psi range.<br /><br />Do not worry about the compression, Charlie. It is okay.

 

[G DANE]

Re: compression number on 73 envinrude????

It is not uncommon to have different compression on the two banks, on many motors they run at slightly different temperature. As JB says, they are within spec. If the difference was over banks there would be more reason to worry.